The present invention is directed to communication systems and techniques thereof.
Over the last few decades, the use of communication networks exploded. In the early days of the Internet, popular applications were limited to emails, bulletin boards, and mostly informational and text-based web page surfing, and the amount of data transferred was relatively small. Today, Internet and mobile applications demand a huge amount of bandwidth for transferring photos, videos, music, and other multimedia files. For example, a social network like Facebook processes more than 500 TB of data daily. With such high demands on data and data transfer, existing data communication systems need to be improved to address these needs. For example, for transmitting a large amount of data, coherent optical systems that utilize high order modulation schemes like 16QAM and 64QAM are being used to satisfy the ever increasing bandwidth demand.
To achieve these high level constellations at high baud rates, imperfections in the transmitter high speed path need to be measured accurately and compensated for, as needed. Gain imbalance and skew between the different coherent transmitter channels are two such impairments. Different techniques exist to compensate for those two particular impairments; some require expensive equipment and long measurement times. Embodiments of the present invention offer simple, fast and sensitive techniques that use relatively inexpensive instruments that are found in many labs and production facilities.